Publications

JOB Pertamina-Seaunion Energy (Limau) Ltd. drilled its first horizontal well in the Q-51 Block of the Limau Oil Field, South Sumatra, Indonesia in September, 1999. The primary objective was to improve production performance and oil recovery from a mature oil field that faces escalating water cuts and production decline. The reservoirs are massive stacked channel / alluvial sandstones, with excellent porosity and permeability, occurring in thick, stackedsand sequences. Water coning in vertical wells has been partially controlled in recent years with reverse coning installations (dual oil-leg/water-leg completions).Reservoir numerical simulation modeling was used to history match existing vertical wells and to forecast production from possible horizontal well locations across the top of the remaining oil pay. A detailed drilling plan was prepared for drilling a horizontal sidetrack through a “window cut in the casing of an existing vertical well. The well was successfully drilled and a 215-meter horizontal section of excellent oil pay was completed open-hole, with an uncemented pre-perforated liner.The well produced clean oil during the first five weeks of production, however, after that, the watercut steadily increased. A bottomhole flowing and shut-in pressure survey was conducted and the test analysis indicated that the pressure drawdown was very low, that only 5-10% of the total pay section was effectively producing, and that the wellbore skin was negative. Later, a mud clean-out job and production logging survey was performed, which showed no improvement and that all of the production was coming from a short section at the toe of the well. It was concluded that the wellbore has encountered a very high permeability layer that is causing the water problem and that it may be possible to close this off. It was also concluded that a completion method allowing more isolation control of the wellbore should be utilized on future horizontal wells of this nature.